1. Field of the Invention
The present invention relates to an apparatus and method for repairing torn or avulsed soft tissue. More particularly, the present invention relates to an apparatus and method for providing a connection between healthy bone or soft tissue and selected other healthy bone or soft tissue to accommodate a stable, secure attachment that selectively immobilizes or minimizes movement of intervening injured soft tissue so that the soft tissue may properly heal.
2. Description of Related Art
A relatively common type of injury, especially in connection with sports, is injury in which soft tissue is torn or avulsed from the bone. This type of injury occurs in connection with many types of orthopedic injuries, such as torn or ruptured tendons and/or ligaments. In the shoulder, this type of injury often takes the form of a torn rotator cuff in which a portion of the rotator cuff tendons tear within themselves or avulse from their insertion into the bone. The present invention has been designed primarily for use in repair of torn rotator cuffs, and the description and discussion below will therefore focus on repair of rotator cuffs and the application of the invention to make such repairs. It will be apparent to those of ordinary skill in the art, however, in view of the following discussion and disclosure, that the present invention may be used for selected other orthopedic applications having similar parameters.
FIGS. 1 and 2 are views of a shoulder with typical torn rotator cuffs. In particular, FIGS. 1 and 2 are superior views of a shoulder with a tear associated with the supraspinatus muscle as it inserts into the humerus. The subscapularis muscle and the coracoid process are also shown in FIG. 1 for reference. The tear 1 shown in FIG. 1 is a simple tear, in which the tear 1 is generally perpendicular to the line of action of the muscle.
In FIG. 2, the tear 1 is more complex than the tear 1 in FIG. 1 because the injury in FIG. 2 has one or more branches 2 of the tear 1 parallel to the line of action of the muscle fibers, in addition to the main tear 1, which is substantially normal to the line of action of the muscle fibers.
In general, a torn rotator cuff, such as those shown in FIGS. 1 and 2, can lead to pain, weakness and loss of function. In many cases, the rotator cuff is repaired by surgically reconnecting the edges of the torn muscle or tendon. Repairs may also include reconnecting the edges of any interstitial tear in the tendons, as well as approximating or reattaching the torn edge of the soft tissue to the bone where it originated. As will be discussed in greater detail below, it is believed that the more common current and previous methods of repairing tears to soft tissue and the avulsion of soft tissue from bone include, but are not limited to, sutures, tacks or screws with spiked washers and staples.
Suture fixation of the tendon is believed to be the most common and classic method for approximating soft tissue to bone, and is generally accomplished by one of two different methods. In the first method, the sutures are typically passed through drill holes in the tuberosities and tied over a cortical bone bridge. In the second method, a suture anchor is typically employed where a device is fixed into a blind bone tunnel. Typically, the suture anchor has a suture eyelet on its trailing end, which provides for passage of suture through it. Recent studies have shown that on the bone side of the repair, suture anchor fixation is equal to or stronger than that of bone tunnels.
In both methods, the soft tissue side may be repaired by proper suture fixation. The torn free edge of the tendon, however, can be poor quality tissue if it is subjected to the degenerative process that is commonly involved in these tears. Some studies have shown that the soft tissue side of the repair when utilizing suture anchors can be the weakest link of the overall repair. A common mode of failure on the soft side of the repair is the result of suture pullout or the pulling of sutures through the muscle or tendon.
In order to lessen the risk of failure from pullout of the sutures from the soft tissue, several studies have been done testing various suture techniques and configurations. The so-called simple suture in which a single pass of the suture is made through the soft tissue is often believed to be the weakest configuration. This is commonly used, however, for arthroscopic repair of a tear because of its simplicity. Other more complicated techniques, such as the modified Mason-Allen stitch generally known to those skilled in the art, call for weaving the suture back and forth in the tissue, accessing the more normal tissue proximal to the tear. While this is a stronger construct, there is a concern of strangulating the tissue with multiple weaves, resulting in necrosis of the tendon. Also, this technique does not lend itself to arthroscopic repair of the tear.
Other methods used to combat the problem of suture tearing through tendon include soft tissue buttons (described in U.S. Pat. Nos. 5,306,290, 5,951,590, 6,074,409, and the “TissueButton” by Arthrex), plates (such as described in U.S. Pat. No. 6,093,201) or washers (such as described in U.S. Pat. Nos. D0404128 and 6,206,886) that increase the effective surface area of the suture contact with the soft tissue and also aid in pressing the soft tissue against the bone at the repair interface. This tendon augmentation has been shown to resist failure perpendicular to the tendon fibers but may not reduce tendon shear parallel to the fibers, which is the failure mode when sutures tear through tendon.
Several other devices and techniques offer an alternative to suture fixation. These include screws, screws with spiked washers, tacks, and staples. Screw and tack fixation has been shown to allow adequate fixation of tendon to bone. The soft tissue side of the repair is addressed by using either a broad flat head as part of the screw as in the “Headed Bio-Corkscrew” by Arthrex, or using a separate spiked washer to engage the soft tissue as in the “Biocuff” by Bionix. Tacks such as the smooth and spiked “Suretac” by Acufex address the soft tissue side identically. Examples of devices in these categories are described in U.S. Pat. Nos. 5,013,316, 5,380,334, 5,601,558, 5,370,661, 6,096,060, 5,167,665, 5,893,856 and 5,013,316. Spiked washer technology (as described in U.S. Pat. Nos. 4,988,351, D0374287, D0374286, D0368777) with screw fixation to bone has a long history in other applications such as knee ligament reconstruction and conceivably offers some advantage in resisting pullout of the screw shank through those tendon fibers parallel to the direction of pull of the tendon. All of these methods are imperfect in that the point of fixation of the soft tissue is generally at the free torn edge, which, as noted above, can be of poor quality.
Security of tissue fixation is arguably the most important element in rotator cuff repair. The soft tissue side of the repair has been shown to be the weak link in the overall repair construct utilizing modern techniques. Current methods of obtaining fixation on the soft tissue side of the rotator cuff repair site appear to be limited in their effectiveness by several factors. The free torn edge of the tendon is relatively poor in quality as it is involved in the degenerative process leading to the tear. Arthroscopically placed simple sutures and all the non-suture devices discussed above gain fixation at this free torn edge. More complicated weaving sutures can overcome this problem by accessing more proximal tissue, which is healthier, thicker and stronger, but, as noted above, this may be at the expense of tissue necrosis and certainly does not lend itself to arthroscopic techniques. An additional concern is the range of motion through which a muscle is expected to function.
FIGS. 3A and 3B are superior views of a shoulder during internal and external rotations. From these figures it may be appreciated that soft tissues may experience wide ranges of motion and therefore may undergo dramatic variations in stresses. In addition to internal and external rotation, the shoulder may be moved through adduction and abduction motions (not shown), creating a wide variation in possible stresses at a particular point. It will be appreciated by those of ordinary skill in the art that a surgical repair of injured soft tissue, such as the tears shown in FIGS. 1 and 2, may require more complex repair methods and systems because of the different requirements at various points along the injured site. It would therefore be desirable to have a device adaptable to varying muscle requirements, and configurable to different attachment points or parts of the body being repaired. Accordingly, in order to overcome the apparent shortcomings of the currently available devices, a device is needed that securely fixes the soft tissue to the bone or other healthy soft tissue while augmenting the initial soft tissue side of the connection.